The Grand Canal is so to say the main road of Venice. It starts on the railway station and goes in form of an S-curve south to the St. Mark’s Square. You can also take the “bus” for that way which takes more or less one hour for the 4km trip. If you happen to be in Venice I recommend you to go at least one way with that bus. You’ll have a good sightseeing tour for a fair price and it’s great to experience Venice with a perspective from the water.